1. Field of the Invention
The invention relates generally to electrical apparatus and more particularly to drawout type circuit interrupters.
2. Description of the Prior Art
Drawout type circuit interrupters, widely used in industrial and electric utility applications, consist of a circuit interrupter including a set of separable contacts removably mounted within an enclosure in a manner similar to a drawer in a file cabinet. When the drawout unit is completely inserted into the enclosure, the separable contacts bridge pairs of terminals connected to electrical loads and sources of electrical energy. Thus when the drawout unit is completely inserted, the separable contacts serve to control the flow of current through the terminals.
For safety reasons, the drawout type circuit interrupter usually includes a mechanism for indirectly moving the drawout unit between a connected fully engaged position and a disconnected disengaged position. However, it is often difficult to tell when the drawout unit is at the extreme of its travel, that is either fully connected or fully disconnected. If not fully connected, arcing or overheating can occur at the point of connection between the separable contacts and the terminals when the separable contacts are closed. In addition, if maintenance is attempted on the drawout unit before it is completely disconnected from the source of electrical energy, severe injury to maintenance personnel can occur. Thus it would be desirable to provide a drawout type circuit interrupter which includes means to positively indicate when the drawout unit is in either the connected or disconnected position. In addition it is desirable to provide an interlock to prevent inadvertent incomplete operation of the drawout unit to either the connected or disconnected position.